The present disclosure herein relates to a decryption method of an encryption algorithm and an encryption system using the same.
Generally, basic functions of cryptographic technologies may be classified into confidentiality functions (referred to as ‘encryption technology’) and certification technologies (referred to as ‘fundamental cryptographic protocol technology’).
The confidentiality function, which is a function of preventing illegal exposure of important data transmitted on information communication network, refers to technology or science that treats principles, means, and methods for transforming messages into indecipherable forms by a third party or converting encrypted messages into decipherable forms.
Normal messages that a transmitter intends to send to a receiver are called plaintexts, and a process of converting plaintexts into ciphertexts that a third party cannot understand is called encryption. On the contrary, a process of recovering ciphertexts to original plaintexts is called decryption. Decryption refers to a case where a legitimate receiver recovers ciphertexts to plaintexts through just procedures, and cryptanalysis refers to a case where an illegitimate third party (e.g., wiretapper) pries plaintexts through other means.
Also, encryption/decryption manners refer to encryption/decryption algorithms, and parameters for controlling conversion of plaintext/ciphertext by the encryption/decryption algorithms refer to encryption/decryption keys. The encryption/decryption algorithms are divided into symmetric key encryption algorithms and public key (asymmetric) encryption algorithms. Data Encryption Standard (DES), U.S. Standard, and SEED, Korean Standard, are representative examples of symmetric key encryption algorithms, and RSA is a representative public key algorithm.